Overexpression and selectively regulatory roles of IL-23/IL-17 axis in the lesions of oral lichen planus

Abstract

Interleukin- (IL-) 23/IL-17 axis is a newly discovered proinflammatory signaling pathway and has been implicated in the pathogenesis of many chronic inflammatory and immune disorders. Here we investigated whether the IL-23/IL-17 axis was present and functional in the lesions of oral lichen planus (OLP), a chronic inflammatory disease affecting the oral mucosa. Using immunohistochemistry and quantitative PCR, we found that the subunits of IL-23 and IL-17 were overexpressed in OLP lesions than in normal oral mucosa tissues. In addition, the expressions of IL-23 and IL-17 are positively correlated in reticular OLP tissues. Results from in vitro studies revealed that exogenous IL-23 could increase the percentage of Th17 cells and IL-17 production in the CD4+T cells from reticular OLP patients. Furthermore, we also found that exogenous IL-17 could significantly enhance the mRNA expressions of β-defensin-2, -3, CCL-20, IL-8, and TNF-α, but not β-defensin-1, CXCL-9, -10, -11, CCL-5, and IL-6 in human oral keratinocytes. Taken together, our results revealed an overexpression pattern and selectively regulatory roles of IL-23/IL-17 axis in the OLP lesions, suggesting that it may be a pivotal regulatory pathway in the complex immune network of OLP lesions.

Figure 1

Immunohistochemical stainings for IL-23p19 (a–f) and IL-17 (g–l) in erosive (a, b, g, and h) and reticular (c, d, i, and j) OLP lesions and normal oral mucosa tissues (e, f, k, and l). Immunohistochemical staining for IL-23p19 showed diffuse and strong patterns in epithelium and the extracellular matrix of the lamina propria of both erosive ((a) ×100; (b) ×400) and reticular ((c) ×100; (d) ×400) OLP lesions, but weak or absent pattern in normal oral mucosa tissues ((e) ×100; (f) ×400). Abundant IL-17 positive staining was observed on the cytoplasm of the infiltrated lymphocytes in the lesions of both erosive ((g) ×100; (h) ×400) and reticular ((i) ×100; (j) ×400) OLP, but only a few sporadic IL-17+ cells were seen in normal oral mucosa ((k) ×100; (l) ×400).

Figure 2

Expressions of IL-23 and IL-17 in OLP lesions. (a) The average staining scores of IL-23p19 in erosive OLP lesions (n = 13), reticular OLP lesions (n = 14), and normal oral mucosa tissues (n = 10). (b) The average number of IL-17+ cells per hpf in erosive OLP lesions (n = 13), reticular OLP lesions (n = 14), and normal oral mucosa tissues (n = 10). ((c) and (d)) The mRNA expressions of IL-23p19, IL-12p40, and IL-17 in reticular OLP lesions (n = 14) and normal oral mucosa tissues (n = 10). All data were shown as mean ± SEM. **P < 0.01; **P < 0.05; NS: nonsignificantly.

Figure 3

Correlation between the expressions of IL-23 and IL-17 in OLP tissue specimens. (a–c) Correlations between the staining scores of IL-23p19 and numbers of IL-17+ cells per hpf in total OLP tissue specimens (n = 27, r = 0.161, P > 0.05), erosive OLP tissue specimens (n = 13, r = 0.012, P > 0.05) and reticular OLP tissue specimens (n = 14, r = 0.559, P < 0.05). (d-e) Correlations between the mRNA expressions of IL-23p19 ((d) r = 0.723, P < 0.01) or IL-12p40 ((e) r = 0.565, P < 0.05) and IL-17 in reticular OLP tissue specimens (n = 14).

Figure 4

The effect of recombinant (r) IL-23 on the percentage of Th17 cells and IL-17 production in CD4+T cells from OLP patients. (a) Representative scatter plots of CD4+IL-17+ staining in peripheral blood CD4+T cells from OLP patients (n = 10), with or without the stimulation of rIL-23 (20 ng/mL) for 36 h. ((b) and (c)) Paired comparisons of percentages of Th17 cells (b) and the IL-17 content in the culture supernatant (c) in peripheral blood CD4+T cells from OLP patients (n = 10), with or without the stimulation of rIL-23 (20 ng/mL) for 36 h.

Figure 5

The effect of recombinant (r) IL-17 to the mRNA expressions of inflammatory mediators, including β-defensins (a), chemokines (b), and proinflammatory cytokines (c), on the HOK cells. Results were shown as mean ± SEM. **P < 0.01; **P < 0.05.

Figure 6

Schematic model of IL-23/IL-17 axis involved in the pathogenesis of OLP. The whole process is divided into three steps: (1) keratinocytes in OLP lesion produce a large amount of IL-23 via an unknown mechanism; (2) keratinocyte-derived IL-23 may contribute to the accumulation of Th17 cells and the overproduction of IL-17 in the local lesion of OLP; (3) IL-17 reversely induces the keratinocytes to selectively produce various inflammatory mediators, which compose the complex immune network in the inflammatory environment of OLP lesions.